This invention relates to packaging machines and particularly to seals for clean-in-place enclosures for packaging machines.
Packaging machines of the form-fill-seal type generally involve the formation of a carton, filling the carton with a product, and thereafter sealing the carton. When the product is a food product, such as juice or milk, the interior of the carton is maintained clean. At the end of a production shift, or at the end of a given production run, or in other instances, it becomes necessary that the portion of the machine which is exposed directly to the product, particularly within a filling station of the machine, be cleaned and/or sterilized. The cleaning operation generally involves flushing clean water over and/or through the components within the filling station, followed by washing with chemicals, in some instances, and sterilization of the cleaned equipment by exposure to a sterilant such as high temperature water and/or a sterilant such as hydrogen peroxide.
Desirably, this cleaning and/or sterilization is accomplished without the disassembly or removal of one or more of the components of the filling station equipment. Following cleaning of the components, the cleaned and/or sterilized equipment is to be maintained clean until the machine is again placed into production. Toward these ends, it is common to encase the filling equipment of a packaging machine within a xe2x80x9cclean-in-placexe2x80x9d enclosure, which in most instances comprises a housing which is capable of being made fluid-tight, and within which the sterilized equipment is housed. During a filling operation, a portion of this housing is open for the movement of cartons into and out of the enclosure, hence through the filling station. This opening through which the cartons pass is provided with a removable cover which, when in place, renders the entire housing fluid-tight.
In a high-speed packaging machine, empty cartons are moved via a conveyor into the filling station at a location beneath one side corner of the enclosure. When so located, the bottom end of the carton is engaged by a lift arm mounted on the end of a first vertically oriented reciprocative lift rod. Substantially simultaneously, the top end of the carton is engaged by a retainer which is mounted on the end of a second vertically oriented reciprocative lift rod, thereby capturing the carton between the lift arm and the retainer. The first and second lift rods move upwardly from the conveyor and move the captured carton into the filling station enclosure. This action is rather dynamic and each carton must be grasped and held substantially stationary within the enclosure.
Within the enclosure, the carton is filled with product. Thereafter, the first and second lift rods are moved downwardly to redeposit the filled carton on the conveyor. Once the filled carton is deposited onto the conveyor, the lift arm and the retainer disengage from the carton and remain in position to engage and move a further empty carton into and out of the filling station enclosure. Each of these reciprocative lift rods passes through the bottom wall of the enclosure. By reason of the high speed of the packaging machine, for example, 150 cartons filled per minute, each rod moves through its reciprocatory cycle at a high rate of travel and a large number of times over a short period of operating time, thereby creating severe wear upon any type of known sealing arrangement between a lift rod and the bottom wall of the enclosure.
During the time that a carton is in the enclosure and being filled, there is no need for sealing between each of the lift rods and the bottom of the enclosure, and in fact, it is most desirable that there be minimal or no frictional drag between a lift rod and any mounting of the lift rods in the bottom wall of the enclosure when the lift rods are in motion. However, for cleaning-in-place of the filling equipment housed with the enclosure, it is required that each lift rod be sealed fluid-tight relative to the bottom of the enclosure to avoid escape of cleaning fluid and sterilant from the enclosure to the ambient environment.
In accordance with one aspect of the present invention, there is provided a novel sealing structure which provides for minimal or no engagement of the seal with a lift rod which is reciprocating within an opening through the thickness of the bottom of the enclosure, but which is selectively actuatable to provide a fluid-tight seal between a lift rod and the bottom wall of the enclosure upon the commencement of a clean-in-place operation for the filling components housed within the enclosure. At noted hereinabove, the opening in the enclosure through which a carton is introduced to and removed from for filling of the carton, is readily closable, fluid-tight, as by a removable cover for this opening. Employing the present invention, no disassembly of any portion of the filling components housed with the enclosure is required, and the required sealing of the spacing between the lift rod and the bottom of the enclosure takes place automatically upon commencement of the clean-in-place operation. In similar manner, upon completion of the clean-in-place operation, either substantially simultaneously, or upon commencement of a subsequent operation of the overall packaging machine, the sealing structure of the present invention may be reversed and the lift rod released to freely reciprocate through the seal associated with the bottom wall of the enclosure.
In a specific embodiment, the sealing structure of the present invention includes a stationary seal plate adapter mounted to the bottom wall of the enclosure, a seal actuator/bearing component, and an annular resilient member, such as an xe2x80x9cOxe2x80x9d-ring, disposed within a radially tapered-wall annular space defined between the adapter and actuator/bearing component and encircling the lift rod passing through the sealing structure. The diameter of the xe2x80x9cOxe2x80x9d-ring is chosen to be greater than the outer diameter of the lift rod which is encircled by the xe2x80x9cOxe2x80x9d-ring. In operation, the xe2x80x9cat restxe2x80x9d xe2x80x9cOxe2x80x9d-ring disengages itself from the outer circumference of the lift rod. Upon actuation, the actuator/bearing component is urged toward the seal plate adapter to thereby reduce the internal volume of the tapered-wall annular space and compress the xe2x80x9cOxe2x80x9d-ring into sealing engagement with the outer circumference of the lift rod, thereby effecting the desired sealing between the lift rod and the bottom wall of the enclosure.